A. Field of the Invention:
The present invention relates to a method and system for protecting the threaded ends of pipes, such as oil field tubular goods, from physical damage and corrosion by providing a thread protecting end caps formed of a polymeric body having a corrosion inhibitor integrally molded therein and having a weather barrier system, and to a method for recycling used end protectors.
B. Description of the Prior Art
Drill pipe, tubing and casing—oil field tubular goods (OFTG)—for oil and gas drilling, completion, production and stimulation activities are typically held in a storage or pipe yard after they have been received from the fabricator or returned from downhole use. A major industry has developed in protection of such oil field tubular goods, also called “tubulars,” to prevent them from corroding during periods of storage. The storage is not permanent, typically extending for a number of months or until a need arises for a specific size and grade of the tubular in question. The tubular goods are typically cleaned before storage in order to prepare them for shipment to the rig site at a future date. However, corrosion due to water and oxygen may quickly attack the precisely machined threads, which then cannot provide a satisfactory threaded connection. Pipe thread corrosion may be ordinary oxidation, or rust, or maybe aggravated by micro-organisms which feed on various materials on the surface of the thread, producing an acid which causes pitting of the threads.
The exposed threaded ends of tubular metal goods are conventionally protected by some sort of supplemental means in order to extend their storage life. For example, physical thread protectors in the form of plastic or elastomeric end caps or end caps made from metals such as steel, brass or copper have been placed on the threaded ends of tubular goods to provide protection from physical abuse and from corrosion. Chemical compositions which act as running compounds and/or corrosion inhibitors are also applied to the thread surface regions of the tubulars, which combined with thread protectors serve to function as a system to prevent impact and corrosion damage to the valuable and vital thread areas. For example, API (American Petroleum Institute) pipe dope (thread compound) is utilized, although it is generally low in corrosion inhibiting properties. Pipe dope is intended to be used as a running thread compound with lubricating and sealing properties. It is a thick grease based material which may contain lead, other heavy metals and filler materials to seal the thread passageways found in the threaded connection of oil field tubular goods. An example of a storage compound as opposed to a thread compound is a product sold under the trademark KENDEX that is a wax based material which is only applied to prevent or inhibit corrosion. Other lighter materials, such as a light oil might be utilized as well if the pipe is to be used within a day or two of the time it is threaded.
While in some cases the applied compounds and solids are captured and recycled, they are sometimes allowed to be discharged into the environment, presenting the problems of hazardous waste containment and removal. Once the tubulars are threaded the manufacturer must apply either a pipe dope or storage compound then apply a thread protector to prevent corrosion and/or impact damage. OFTG threads are frequently subjected to a series of inspections once shipped from the manufacturer. These inspections require the removal of the thread protector and the applied compound. The compound on the thread protector and the threaded ends must be treated as hazardous waste and therefore present an expensive containment and removal problem.
Pipe dope compositions are less than an optimum solution as a storage compound since these products do not offer sufficient anti-corrosion properties and often contain hazardous materials such as lead, copper, zinc, and hydrocarbons. Storage compounds cannot be used as an API thread running compound as they do not exhibit sufficient lubricity properties, sealing properties and must be cleaned from the threaded connection thoroughly before the API thread compound and sealant is employed.
The mechanical end caps or thread protectors have traditionally functioned primarily to protect the threads against impact damage if the pipe is accidentally dropped or bumped. Many of the prior art thread protectors are loose fitting “dust covers” and are of little value in preventing impact damage or the intrusion of moisture into the thread region. Certain of the prior art designs are “cup-shaped” and thus offer a tighter fit and incorporate moisture seals, such an O-rings, in an effort to improve corrosion protection.
The prior art end caps are generally removed near the well site and often are contaminated with immersed crude oil, pipe dope, drilling mud and accumulated tars and lighter oils that are found on the drill site. As a result, recycling the plastic or elastomeric polymers making up the prior art end caps has been economically unfeasible in many instances due to the cost of cleaning the waste polymer pieces for recycle processing.
A need exists for an improved end cap for protecting the threaded ends of oil field tubular goods from physical damage and corrosion which eliminates the need for pipe dopes, greases, heavy metal constituents, or hazardous materials used in the past.
A need also exists for such an end cap which has incorporated therein a corrosion inhibiting compound, the compound being integrally molded within the polymeric body.
A need also exists for an improved end protector composition which can be easily and economically recycled by eliminating the need of much of the cost of cleaning waste polymer pieces before recycle processing.